1. Field of the Invention
The present invention relates to, inter alia, diagnostic imaging systems, and, in particular to a diagnostic imaging system using multiple modalities. More particularly, some preferred embodiments of the invention relate to methods and apparatuses for the using of digital X-ray and gamma camera modalities in the same diagnostic imaging system.
2. Background Discussion
Medical imaging systems are designed to operate in a number of imaging modalities. Examples of different modalities include simple planar x-ray, Computed Tomography (CT), angiography, simple planar imaging by gamma ray cameras, Single Photon Emission Computed Tomography (SPECT), Position Emission Tomography (PET), and others. The particular characteristics of each modality lend themselves to particular applications.
Diagnostic imaging systems which use multiple imaging modalities have been and continue to be developed. These multimodality systems can yield synergistic advantages above and beyond just the advantages of each specific modality. For example, it is known in the art advantage is gained by combining SPECT and CT in a dual-modality system with each mode mounted on separate gantries with the patient supported and transported between them. Such a system allows for more accurate fusion of structural (anatomical) CT data and functional (disease) SPECT data due to decreased patient movement. Spatial image fusion of conventional CT with SPECT often are inaccurate due to patient motion during the long SPECT data acquisition period. Moreover, the lack of a common gantry increases error in the fusion of the structural (anatomical) and functional images. This problem is exacerbated by the use of traditional-style cylindrical CT detectors, which contributes to vibration and other motion, further degrading image fusion. Cylindrical CT detectors are used to perform spiral CT scans. Furthermore, such cylindrical CT detectors are bulky and expensive.
A further problem is that as the CT data have to be taken either before or after the SPECT data are acquired, the conventional CT combined with SPECT cannot realize image registration in time domain, which limits the usefulness of the system in many motion related clinical studies. For example, in cardiac studies, image registration for image fusion is difficult due to the motion of the heart.
Alternative x-ray detectors using solid state systems are available. Such solid states systems use semiconductors such as amorphous silicon. Other systems have been proposed which use overlapping layers to detect both emissive and transmitted radiation. However such overlapping layer systems have questionable sensitivity and resolution.
There remains a need in the art for a system which takes advantage of the advantages of image fusion using a common gantry and detectors with common geometry, which can promote motion related clinical studies while avoiding the problems of a size and cost problems of a cylindrical CT detector.